Halogen Doping Mechanism and Interface Strengthening in the Na₃SbS₄ Electrolyte via Solid-State Synthesis

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• All-solid-state sodium-ion batteries require high-performing sodium solid electrolytes (SSEs) for ambient temperature operation.
• Sulfide solid electrolyte Na3SbS4 (NBS) offers good chemical stability and low-cost synthesis but has limited conductivity when prepared via liquid-phase methods.

Purpose of the Study:

• To improve the ionic conductivity and battery performance of Na3SbS4 by introducing halogen doping.
• To investigate the structural and electrochemical effects of doping NBS with chlorine, bromine, and iodine.

Main Methods:

• Synthesis of halogen-doped Na3-xSbS4-x (M = Cl, Br, I; 0 ≤ x ≤ 0.3) via a solid-state method.
• Characterization using X-ray diffraction with refinement analysis and Raman spectroscopy.
• Testing of symmetric sodium batteries with Na2.85SbS3.85Br0.15 and pristine Na3SbS4 at room temperature.

Main Results:

• Halogen doping, particularly with bromine, was shown to enhance the ionic conductivity of Na3SbS4.
• The symmetric sodium battery using Na2.85SbS3.85Br0.15 demonstrated stable cycling for over 100 hours at 0.1 mA/cm².
• Structural analysis revealed the impact of halogen incorporation on the crystal structure and Na+ ion transport pathways.

Conclusions:

• Solid-state synthesis and halogen doping are effective strategies for developing advanced SSEs.
• Bromine-doped Na3SbS4 presents a promising material for stable and efficient all-solid-state sodium-ion batteries.
• This work provides a pathway for manufacturing novel SSEs by optimizing halogen doping in NBS.